This application relates to an apparatus and method for monitoring substation disconnects and transmission line switches. More particularly, it relates to an apparatus and method for continuously monitoring temperatures of substation disconnects and transmission line switches.
Substation disconnects and transmission line switches are used to physically disconnect circuits to ensure that there is no electrical connection. There are different types of switches, some which rely on rotation of an arm, FIG. 1, and others where the arm rotates around a pivot point at one end of the arm, FIG. 2. The electrical connection between the two sides of the switch is made by the arm making electrical connection into “jaws”.
When an operator closes a disconnect and the arm fits into the jaws, the operator has no way of knowing if the disconnect is fully closed or, if the arm has passed its optimum point. Instead, the operator relies on mechanical stops. Not fully or under closing of disconnects are one reason for overheating.
If proper contact between the arm and jaws is not achieved, high resistance connections may result. With high currents, this connection may overheat and result in degradation of the jaws which may result in failure—catastrophic or nearly impossible to open the disconnect switch. See FIG. 4.
Infrared inspections are the most common methods of identifying high risk disconnects. However, there are some drawbacks: (1) heating only happens at times of high loading—which may not be at the time of inspection; (2) inspections are generally performed one or two times per year; (3) only severely degraded units are identified as small temperature differences are hard to identify and diagnose.